1. Gasoline Direct Injection (Lean Burn) Technology

2. Development of GDI
It was not until 1996 that gasoline direct injection reappeared in the automotive market. Mitsubishi was the first with a GDI engine in the Japanese market with its Galant/Legnum's 4G93 1.8 L I4.[5] It was subsequently brought to Europe in 1997 in the Carisma,[6] although Europe's then high-sulphur unleaded fuel led to emissions problems, and fuel efficiency was less than expected.[7] It also developed the first six cylinder GDI powerplant, the 6G74 3.5 L V6, in 1997.[8] Mitsubishi applied this technology widely, producing over one million GDI engines in four families by 2001.[9]
PSA Peugeot Citroën, Hyundai and Volvo licensed Mitsubishi's GDI technology in 1999, with Hyundai building the first GDI V8.[10][11] Although other companies have since developed gasoline direct injection engines, the acronym 'GDI' (with an uppercase final "I") remains a registered trademark of Mitsubishi Motors.[12]
In 1998, Toyota's D4 direct injection system first appeared on various Japanese market vehicles equipped with the SZ and NZ engines.[13][14][15] Toyota later introduced its D4 system to European markets with the 1AZ-FSE engine found in the 2001 Avensis.[16] and US markets in 2005 with the 3GR-FSE engine found in the Lexus GS 300. Toyota's 2GR-FSE V6 uses a more advanced direct injection system, which combines both direct and indirect injection using two fuel injectors per cylinder, a traditional port fuel injector (low pressure) and a direct fuel injector (high pressure). This system known as D-4S or D4 Superior first appeared in the US with the launch of the Lexus IS 350. 2

3. Development of GDI
In 1999, Renault introduced the 2.0 IDE (Injection Direct Essence),[17] first on the Megane and later on the Laguna. Rather than following the lean burn approach, Renault's design uses high ratios of exhaust gas recirculation to improve economy at low engine loads, with direct injection allowing the fuel to be concentrated around the spark.[18]
In 2000, the Volkswagen Group introduced its gasoline direct injection engine in the Volkswagen Lupo, a 1.4 litre I4 unit, under the product name "Fuel Stratified Injection" (FSI). The technology was adapted from Audi's Le Mans prototype race car R8. Volkswagen Group marques use direct injection in its 2.0 L FSI turbocharged and naturally-aspirated four-cylinder engines. Later, a 2.0 litre I4 unit was introduced in the model year 2003 Audi A4. All new petrol engines from the mainstream marques of Volkswagen Group now use this FSI technology.
PSA Peugeot Citroën introduced its first GDi (HPi) engine in 2000 in the Citroën C5 and Peugeot 406. It was a 2.0-liter 16-valve EW10 D unit with 140 hp (104 kW), the system was licensed from Mitsubishi.[10]
In 2001, Ford introduced its first European Ford engine to use direct injection technology, badged SCi (Smart Charge injection) for Direct-Injection-Spark-Ignition (DISI). The range will include some turbocharged derivatives, including the 1.1-litre, three-cylinder turbocharged unit showcased at the 2002 Geneva Show.
In 2002, Alfa Romeo introduced its first direct-injection engine, the JTS (Jet Thrust Stoichiometric),[19] and today the technology is used on almost every Alfa Romeo engine. 3

4. Development of GDI
In 2003, BMW introduced a gasoline direct injection V12 N73. This initial BMW system used low-pressure injectors and could not enter lean-burn mode, but the company introduced its second-generation High Precision Injection system on the updated N52 straight-6 in This system surpasses many others with a wider envelope of lean-burn time, increasing overall efficiency.[20] In 2007, BMW released the new N54 twin-turbo-charged direct injection engine for its 335i Coupe and later for the 335i Sedan, 535i series and the 135i models.[21] PSA is cooperating with BMW on a new line of engines which made its first appearance in the 2007 MINI Cooper S.
Since 2004, General Motors has released three such direct injected engines: in 2004, a 155 hp (116 kW) version of the 2.2 L Ecotec used in the Opel/Vauxhall Vectra and Signum;
In 2005, Mazda began to use their own version of direct-injection in the Mazdaspeed 6 and later on the CX-7 sport-utility, and the new Mazdaspeed 3. It is referred to as Direct Injection Spark Ignition (DISI).
In 2006, Mercedes-Benz released its direct injection system (CGI) on the CLS 350 featuring piezo-electric fuel injectors.
In 2007, Ford introduced its new Ford EcoBoost engine technology. The engine first appeared in the 2007 Lincoln MKR Concept under the name TwinForce. The new global EcoBoost family of 4-cylinder and 6-cylinder engines features turbocharging and direct injection technology (GTDI - Gasoline Turbocharged Direct Injection). A 2.0-litre version was unveiled in the 2008 Ford Explorer America Concept. 4

5. Lean Burn
Engine which can operate in very lean A/F mixture are called "Lean Burn Engines".
The leaner A/F mixture, the more economical the engine is.
But there are two reasons that prevent the conventional engines from operating in lean A/F mixture:
If the mixture is too lean, the engine will fail to combust.
Naturally, lower fuel concentration leads to less output. 5

6. Stoich VS Lean Burn Stoichiometric 14.7:1 455:31 Homogeneous Lean Burn
37.9:1
455:12
Knocking 6

7. What Make it Possible?
Lean burn engines avoid these problems by adopting a highly efficient mixing process.
They use special shape pistons, with intake manifold located and angled matching the pistons, the intake air will generate swirl inside the combustion chamber.
Swirl leads to more complete mixing of fuel and air, thus largely reduce the badly-mixed fuel particles, which will not be burnt in conventional engines.
This enables more complete burning, not only reduces pollutant, but also allow the A/F ratio to be lowered from 14 : 1 to 25 : 1 without altering the output.
Today, Lean Burn technology has evolved into Direct Injection, which is basically the former added with direct fuel injection.

8. Gasoline Direct Injection (GDI)
GDI consumes 20 to 35% less fuel, generates 20% less CO2 emission and 10% more power than conventional engines.
Direct injection has been used in diesel engines for many years, but not in petrol engine.
Unlike conventional engines, GDI uses upright straight intake port, accompany with a concave-section piston surface.
Swirl air flow will be generated during compression stroke.
When fuel directly injects into the combustion chamber, the swirl helps mixing air with fuel.
It pumps out the fuel at higher pressure, enables better vaporization and more uniform spread.
GDI engine has an extraordinarily high compression ratio of 12.5. 8

9. GDI Cont.
Main injection takes place as the piston approaches top dead centre on the compression stroke, shortly before ignition.
The concave-section piston concentrates more fuel around the spark plug, this allows successful ignition without misfire even when the A/F mixture is very lean.
This explain why GDI can operate under A/F ratio of 40 : 1 under light load, which is even leaner than Lean Burn Engines.
As a result, more complete burning is achieved. 9

10. Stratified Combustion
Homogeneous Lean Burn 37.9:1 (Impossible)
Stratified Lean Burn
45.6:1 (Possible) 10

11. Reduce Pumping Lost
Driving at km/h did not require throttle plate to widely open (Wide Open Throttle). Throttle will always half close. This will restrain the flow of air to enter the combustion cylinder.
GDI Engine usually remove the throttle plate component. Therefore, reduce the pumping losses.
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12. Cooling Effect of Fuel Injection
Fuel that directly injected into the combustion cylinder will evaporate. The evaporation process will absorb energy from surrounding and reduce temperature inside the combustion cylinder.
Reduction of temperature inside the combustion cylinder can allow higher compression ratio engine design that will increase efficiency of the engine.
                                            
Piston of a 3.5 L Ford EcoBoost engine 12